Anne Barker and Lucia Stein – Experts fear Indonesia, considered one of the world's COVID-19 epicentres, is now a high-risk "hotspot" for the emergence of a new coronavirus "super strain".
An alarming second wave in the country has been largely fuelled by the highly infectious Delta variant, which was first identified in India's out-of-control outbreak.
And now experts are worried that a similar situation could occur in Indonesia, where the rampant spread of the virus may create the perfect breeding ground for another variant of concern.
"Uncontrolled epidemics are really bad hotspots for the evolution of variants," Aris Katzourakis, a professor of evolution and genomics at Oxford University in the UK, said.
"Two of the most challenging variants that we're facing – Alpha and Delta – are quite possibly connected to very poor public health interventions [in the UK and India].
"Controlling the epidemic [in Indonesia] is certainly a high priority for minimizing the risk of a new variant."
As a second wave of the coronavirus has swept through Indonesia's densely populated Java island and Bali in recent months, the hospital system buckled under the pressure of an influx of cases.
With medical resources stretched to their limits, desperate relatives have struggled to obtain oxygen tanks for family members struggling to breathe in hospital.
Others who have tested COVID-positive have been turned away from hospitals, having been asked in some cases to self-isolate in small, often crowded, homes.
The result has been a tragic loss of life, with the death toll in Indonesia surpassing 100,000 since the pandemic began. A staggering 40 per cent of them have been in the past five weeks alone.
Total infections in the fourth most populous country in the world have passed 3.5 million.
The closely watched Indonesian 'variant of concern'
Already one Indonesian 'variant of concern' has spread to neighbouring Malaysia, which currently has one of the fastest infection rates for COVID-19 in the world.
Health authorities in Malaysia's Sarawak state last month identified seven new cases of the B.1.466.2 variant, which was first identified in Jakarta last November.
"Two cases of Beta variant and four Indonesian 'variants of concern' have been identified in Kuching, in Sibu (2) and one case in Bintulu," Dr David Perera, Director of the Institute of Health and Community Medicine at Universiti Malaysia Sarawak, said.
The head of Jakarta's Eijkman Institute for Molecular Biology says the Indonesian variant is being closely monitored.
But he denies it is a "variant of concern" under World Health Organization terminology.
"Not VOC nor VOI (variant of interest)," Professor Amin Soebandrio told the ABC. "However, we have to watch it carefully."
Could we see a 'super strain' emerge out of Indonesia?
While there could be thousands of different versions of the coronavirus currently circulating around the world, many of them won't rise to the level of the Delta variant or have much impact on raging outbreaks.
As quickly as they can emerge, some can just as quickly fade away.
But now and then a virus has a breakthrough and, in doing so, it can change the course of the pandemic.
"[Mutations] become the virus of the day because they take over, because they infect people more easily," public health epidemiologist Dr Emma Miller at Flinders University told the ABC.
"You'll find there have been other ones that have come before Delta – obviously from Alpha through the alphabet to Delta – but Delta has taken over because of its ability to escape, to get as many people affected as possible.
"And that's the raison d'etre of the virus in a population."
Epidemiologist Dicky Budiman says the high positivity rate in Indonesia, or the percentage of people testing positive to COVID-19, as well as the uncontrolled nature of the pandemic, are signs that a new "super strain" could emerge in Indonesia."It's only a matter of time," Mr Budiman, who also advises the Indonesian government on its pandemic strategy, said.
Mr Budiman pointed to Indonesia's experience of bird flu in 2007 and 2008 – when the country had "the most dangerous strain in the world at that time" – as one example.
"It's not impossible. It might well happen in Indonesia," he said.
Professor Katzourakis agrees that it's "right to pick out Indonesia as a possible hotspot" and says it is "completely reasonable" to expect more virulent variants to arise over the coming year.
"If a new virulent strain arises in Indonesia, or arrives in Indonesia, it could challenge Delta," he said.
How vaccines present a challenge to coronavirus mutations
Epidemiologists and health experts agree that the more the virus spreads in a population, the more mutations will occur and the higher the risk of new variants emerging.
This is happening all the time and the majority are "meaningless," according to Dr Peter Drobac, a global public health specialist and Director of the Skoll Centre for Social Entrepreneurship in the UK.
But only when a mutation gives the virus a competitive advantage against other variants, does it potentially take hold in the population and become a more dominant strain, like the Delta variant has done, he said.
Such an advantage could be a variant with more resistance to vaccines.
As more people within a country become immune, either through innoculations or catching and recovering from COVID-19, the more favourable it is for the virus to evolve and find ways around that immunity.
This is known as immune escape.
But for that to happen, experts say a higher level of the population would need to be immunised. Indonesia, with just 7.9 per cent of its population fully vaccinated, doesn't meet this threshold.
"Where you have a good chunk of the population who are vaccinated, and you have the virus spreading like wildfire in the unvaccinated population, those two things together probably create more ideal conditions for a potentially vaccine-resistant variant to emerge," Dr Drobac said.
"If we were particular about selecting for a vaccine-resistant variant, it's more likely to be in a place where a significant portion of the population is vaccinated, but you still have a lot of unvaccinated people getting infected.
"So what's happening in the UK right now might be sort of the most ideal conditions."
'Worst-case scenario' a vaccine-resistant variant
According to the CSIRO's COVID-19 Project Leader Professor Seshadri Vasan, at least one more variant of concern will be declared before the end of 2021, "and it could emerge anywhere".
The "worst-case scenario", in Dr Drobac's view, would be if a vaccine-resistant variant were to take hold.
"That doesn't mean 100 per cent vaccine resistant, but one that is able to bypass vaccines or immune protection much more than Delta.
"If that were the case, all of the vaccinated people who are relatively protected against other variants, would then be vulnerable hosts to a new variant."
But according to Dr Drobac's assessment, the chances of a new variant being more contagious than Delta are relatively low.
"Right now, Delta is so transmissible that it would be hard for a new variant to out-compete Delta on transmissibility, on spreading easily," he said.
"It would probably have to be another advantage."
What has also been promising is that newer vaccines have withstood all four variants of concern in tests at the Australian Centre for Disease Preparedness, according to Professor Vasan.
"We don't yet have a SARS-CoV-2 variant of high consequence that significantly reduces the effectiveness of prevention or medical countermeasures," he said.
"My hope is that before we face that situation, we should get a majority of the world's population fully vaccinated.
One thing most health experts agree on is that the SARS-CoV-2 virus that causes COVID-19 is not going to disappear.
"It's likely to become endemic, meaning it will be circulating through the world all the time, just like influenza is circulating all the time," says Dr Drobac.
"There are new strains that we need to think about each year. I'm not saying that's going to be the case for COVID-19, but it's likely that we will continue to be living with it.
"It will continue to mutate. And that means constant surveillance as well as constant updating of vaccines – and the potential for us needing to have periodic boosters that might address new variants – very likely."